Is there a noticeable pattern in e-mail response behaviour? Can you collect 16 billion messages from 2 million users of the internet and analyze them in a reasonable period manually? No one may attempt such a humongous exercise. But it is possible in the digital world.

On March 1 this year Scientific American reported on such an interesting piece of research. Researchers got some clues about e-mail response patterns by analyzing 16 billion e mail messages sent by 2 million users of Yahoo mail. The researchers at the University of Southern California and Yahoo Labs, used algorithms to mine the data about the times messages were sent and the number of words they contained, among other factors.

They used anonymized data to carry out the largest ever analysis of email behavior .

The younger you are, the faster and more terse your reply (box at bottom).

Messages sent on weekday mornings got the fastest responses.

E-mails with attachments took twice as long to get a reply as those without.

The researchers included only those users who wrote to one another at least five times in the months covered by the study period.

They found that they could use their algorithm to predict when an e-mail conversation was nearing its end. For the first half of a dialogue, correspondents usually developed similar reply times and e-mail lengths, lobbing messages back and forth at a regular clip. Yet that similarity decreased as the conversation trailed off. Many conversations ended with a long lag before one correspondent sent a final brief reply.

Ms Greenwood noted that “the more words in a reply, the longer it tended to take for the writer to send it—but only up to 100 words. Beyond that, the time for a reply actually dropped slightly, except for in the oldest age group”.

“So if you’re expecting a hefty reply to your mission-critical missive, it won’t necessarily take any longer than a 100-word message. That may be some comfort while you wait on the edge of your seat”, she concluded .